In the semiconductor industry, semiconductor wafer materials are annealed, so that dopant atoms, such as boron, phosphorus or arsenic, etc., can diffuse into substitutional positions in the crystal lattice, resulting in changes in the electrical properties of the semiconducting material.
Silicon has been found to evaporate from SiC when annealed at the temperatures required to activate nitrogen implants for n-type or aluminum for p-type SiC. To counter this problem, AlN or BN caps were found to prevent SiC decomposition up to 1600° C. in a nitrogen atmosphere.
However, implantation activation in the Group III nitride materials semiconductors, such as gallium nitride (GaN), is more difficult than with elemental semiconductor materials. In fact, it is well-publicized that Group III nitride materials decompose by preferential evaporation of nitrogen when annealed at high temperatures, because of the high vapor pressure of nitrogen.
It has been shown that silicon implants may be activated to make III-Nitride n-type by annealed in a Rapid Thermal Annealer (RTA) at high temperatures for short periods of time if capped with a capping layer of SiO2, Si3N4 or AlN. Sequential short RTA processes have been used to activate implants while limiting decomposition. High nitrogen over-pressure annealing can be used, but it requires specialized equipment to deal with dangerous pressures at high temperatures.
Accordingly, improvements for annealing Group III nitride semiconductors would be useful.